DE 34 48 026 C2 and DE 34 24 257 A1 already describe apparatuses for controlling the outlet width for the production of treads for car tires or other profiles or webs made of rubber, elastomers or thermoplastic material, consisting of a nozzle, arranged at the material outlet of a screw extruder provided with a drive, for profiling the material. The nozzle outlet is formed by a housing part formed having a replaceable profile bar and by a rotating roller equipped with a drive and arranged perpendicular to the nozzle outlet. By means of hydraulic cylinders and the associated supports, the exchangeable profile bar is held securely in its positions.
In practice, extruder heads of this kind, also referred to as single-roller heads, are often already used for the production of vehicle tires, for example. A plasticized rubber mixture is fed into the extruder head and preshaped across the whole production width. In the extruder head there are replaceable bars which, at the outlet to the roller gap, ensure the exact adjustment of the extruder head opening to the given web thickness.
The use of such apparatuses is mainly suitable for profiles which have a rectangular cross-sectional surface, for example smooth sheets and webs, and for profiles without undercuts, for example profiled products. It is possible in this way to achieve a high degree of uniformity of the material thickness over the whole width of the web and a high degree of homogeneity of the rolled profile.
DE 691 10 246 T2 is equipped with both a roller pair and an extrusion bar. The rubber output from the nozzle opening is rolled and shaped between an upper roller and a lower roller.
Considerable advantages of single-roller head devices are mainly the low tool costs for the extrusion bar, the short retooling times on account of simple tool changeover, their suitability for complicated profile shapes, in particular valley profiles, and the lower investment needed for devices of this kind.
In practice, a disadvantage has been found to be the customary fixing of the bar by means of clamping, where the direction of action of the fixing force pushes obliquely on the bar. In this way, during the fixing process it is possible to unintentionally move the bar relative to the bearing surface and as a result the gap may, in deviating from its intended position, have an undefined size or may be pretensioned against the roller in an undefined manner.